Castable machine tool bit composition of boron carbide and nickel



United States Patent 3,386,812 CASTABLE MACHINE TOOL BIT COMPGSITION 0FBORON CARBIDE AND NICKEL Haskell Sheinberg, Los Alamos, N. Mex.,assignor to the United States of America as represented by the UnitedStates Atomic Energy Commission N0 Drawing. Filed Dec. 23, 1965, Ser.No. 516,148

2 Claims. (Cl. 29-1818) ABSTRACT OF THE DISCLOSURE A machine tool bitcomposition and method for making same in which 80 v/o Ni-20 -v/o B.,Cpowders are mixed, pressed and heated to a temperature of about 1530 C.in argon or H gas atmosphere.

The present invention relates to a machine tool bit composition and,more particularly, to an extremely hard composition which is castableutilizing conventional furnaces. The invention described herein was madein the course of, or under, a contract with the US. Atomic EnergyCommission.

The extra hard tool bits which are presently in use (about 1100 DPH)have very high melting temperatures and are consequently shaped bypowder metallurgy techniques. It would be advantageous to develop a veryhard tool bit composition which can be melted at fairly low temperaturesso that the bit would be castable.

Accordingly, an object of the present invention is to provide acomposition suitable for an extra hard tool bit which may be formed bycasting.

The invention is based on the discovery that heating 80 W0 Ni-20 v/o B Cpowders to about 1530 C. in argon or H gas yields a low melting pointcompound of extreme hardness (1100 DPH).

In one specific embodiment, 5.02 g. B C (nominally -100+230 mesh) wasblended with 71.2 g. Ni which is approximately 7 w/o B 093 w/o Ni(Fisher average particle sizes3.9 microns) for 4 hrs. in a bottle withaluminum agitator wires. The blended mixture was then pressed in a l-in.I.D. steel die at 19 tons/sq. in. to a density of 68% of theoretical.The pressed piece was sintered in a clean alumina boat in a Bell jartype furnace at 1530 C. (optical) for approximately 10 minutes 3,386,812Patented June 4, 1968 ice under argon. In another specific embodiment7.53 g. B C (-120-1-200 mesh) was blended with 106.6 g. Ni which isapproximately 7 w/o B C-93 w/o Ni (Fischer average particle size3.9microns) for 4 hrs. with aluminum agitator wires in a bottle. Theblended mixture as then pressed in a l-in. x 3-in. steel die at 16 /2tons/sq. in. to a density of theoretical. The pressed piece was heatedin a clean alumina boat in a tube furnace at 1530 C. for 25 minutes in HClearly, the material could be cast and formed simultaneously sincemerely heating forms the desired compound. Stirring of the materialwould be a desirable feature but is in no way necessary.

Even though the B C is an exceedingly high melting point compound, thereaction is quite fast (less than onehalf hour) and fine grains areformed. In addition the resulting composition is fully dense and ofuniform structure, i.e., there is about the same amount of matrixmaterial around all particles. The precise structure of the resultingmaterial is not known at this time but is felt to be a nickel richboride (or carbide) with a carbide precipitate at grain boundaries.

What is claimed is:

1. A method of forming a composition consisting essentially of mixing 93w/o Ni and 7 w/o 13 C powders, pressing, and heating to about 1530 C. inan environment selected from the class consisting of an inert andreducing atmosphere.

2. A casta'ble machine tool bit composition consisting of approximately93 w/o Ni, the balance being B C.

References Cited UNITED STATES PATENTS 2,124,538 7/1938 Boyer --204-3,178,807 4/1965 Bergmann 75204 3,306,741 2/ 1967 Lallemant 75-204 OTHERREFERENCES Refractory Hard Metals, Schwarzkopf et al., Macmillan 00.,New York, 1953, p. 412.

CARL D. QUARFORTH, Primary Examiner.

L. DEWAYNE RUTLEDGE, Examiner.

R. L. GRUDZI-ECKI, Assistant Examiner.

